Ion implantation is a standard technique for introducing material into a workpiece. A desired implant material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the ion beam penetrate into the bulk of the workpiece material and affect both the surface and depth of the workpiece material under certain conditions.
Gallium nitride (GaN) is a material commonly grown on workpieces. GaN is becoming more important for use in light-emitting diodes (LEDs), power transistors, and solid state lasers. The ability to grow high-quality GaN is one limiting factor to improving the quality and lowering the cost of these devices. One method of improving the quality of epitaxially-grown GaN is known as epitaxial layer overgrowth (ELOG). For ELOG, a layer of GaN is grown, hard mask windows of SiO2 or SixNy are deposited, and then the high-quality GaN is grown. In some instances, deposition of the hard mask requires removal of the workpiece from the MOCVD tool and then reintroduction of the workpiece to the MOCVD tool after a lithography step, photoresist application, deposition, and photoresist removal. This particular process is cumbersome and costly. Repeated ELOG sequences add even more cost.
FLOG of GaN on silicon, sapphire, SiC, AlN, GaN, or other workpieces can be accomplished using implantation instead of SiO2 or SixNy deposition. Previously, photoresist was used to mask part of the silicon workpiece and implantation was performed on the unmasked areas. GaN grew laterally over the implanted areas. However, this process is still fairly complex. The use of photoresist adds extra steps, which increases manufacturing costs. What is needed is a faster, less complex, and lower cost method of growing high-quality compound semiconductor layers.